Healthy vs Diseased Transport and Mixing in the Human Left Ventricle

It has become increasingly clear that the dynamics of the left ventricle (LV) plays a major role in dictating overall cardiac health. Phase-contrast magnetic resonance imaging (PCMRI) and Doppler-ultrasound echocardiography can measure flow characteristics inside the human left ventricle in vivo, including diagnostic data useful for evaluating pathological conditions such as cardiomyopathies. Studying these flow patterns is a potential avenue for heart failure diagnosis. Traditional studies based on Eulerian measures computed from instantaneous velocity data, e.g. streamlines, vorticity, Q-criterion, etc., can be insufficient or unreliable to fully understand unsteady blood flow behavior. We used the Finite-Time Lyapunov Exponent (FTLE) approach to compute Lagrangian coherent structures (LCS) to gain insight into how blood is transported inside the LV. LCS can be thought of as special moving boundaries in the flow that partition regions with different dynamics, and whose coordinated motion organizes transport and mixing.